This bottle, first shown during Negi's flashback in his mind-synchronization with Asuna, and then later in the battle against Wilhelm, is used as a container for sealing demons. The bottle was first shown being used by Stan to protect a then four year-old Negi from Wilhelm and the Slime Trio. When Wilhelm and the Trio were released, they kept the bottle with them, and it was stolen by Kotarou after a short fight with them. Negi tried to use the bottle to re-seal Wilhelm, but the magic was deflected by the pendant Wilhelm placed on Asuna in order to use her magic-cancelling ability for his own protection. Yue and Nodoka would later use it to seal the Slime Trio.